Is Is Compressor Surge?

[iplen]

Have just finished fitting GT2860-9s to my car, when cruising along in 5th at 100ish going up hills with light load it starts making a sound like a steam train, it does not surge power wise, but it just makes this noise for as long as I hold it on light throttle, so I back off, it stops, accelerate, still not there, lift off to hold 100k, it starts again.. It did used to do the same with stock turbos but rarely, and not as bad.

Questions:

Is it compressor surge?

Apart from being bloody annoying is it doing any damage?

With a PFC and a tune will it be possible to get rid of it? (or what will?)

[StealthX]

Sure it's not just induction noise? Post a video of it?

Doesn't sound like anything to worry about, just you can hear it now cos these turbos are bigger than the stockies.

[zebra]

Its a typical GTR problem, but my soarer also does it sometimes,

Its because the Dash-9s in your case want to spool up very quickly, but the engine cant swallow it so it spits the excess air back out the turbo inlet, which slows 1 turbo down as the air comes back out then vice versa with the 2nd turbo.

Do you have the standard Bovs on the car or aftermarket ones? the standard ones are always open when the intake is under vacume to help prevent this.

[GTScotT]

Is it a weird sort of flutter noise? Choo choo choo choo??

If so, probably turbo shuffle

[R31Nismoid]

What...

BOV setup?

Intake piping setup?

They shouldn't surge, the -5's/GT-RS flow more and are known for it in certain conditions

[EdGTR]

hey mate yeah mine does exactly the same thing ive got gtss(same same -9) apexi intake and still have the standard bovs. Mine does it at zero vacuum and i was thinking that it was the bovs opening a little and air flowing through them but i havnt tested this theory. i might have a play next week.

I dont think its anything to worry about but up a slight hill it can be a bit annoying.

[EdGTR]

Yeah mate i just spoke to my shop and he has a couple of aftermarket bovs that i want to try and it should tell us whats going on. ill have a look late next week and write up what i found.

[iplen]

Apexi pods and turbos are the only mods, does it on any boost setting (7,12,18). Turbo shuffle sounds far more likely, that is the noise I am getting, remember hearing talk about it previously but had forgotten until GTScotT mentioned it. Definately not the induction noise.

[R31Nismoid]

Aftermarket BOV's will only make it worse.

[Don Dada]

7psi?...What actuators did u use?

[iplen]

Actuators are the Garrett ones that came with the turbos

[pistol-pete]

does it go away when you put your foot down? my -5's with apexi pods do the same sort of thing at around 3.5-4k, i think its just something to do with the way the exhaust housing is designed.

[iplen]

Sometimes goes away when I put my foot down, sometimes continues. Any idea whether this can be tuned out of them? would imagine not but have seen good tuners do some impressive things

[paulr33]

can u put more preload or tighten the bovs?

i think the bov's are opening on light throttle load - dont know why tho

[jimboppins2230]

check your gaskets.

i had a similar lawnmower noise at light load.

blown turbo gasket.

[marksuxass]

This basically happens when the engines displacement is too small for the turbo application. What you need to do is think of it a little like this. An rb26 with twin turbos is essentially like having x2 1300cc displacement engines with single turbos on each (which in most cases is too large for the displacement. As you can imagine as you increase the turbo size (say gtrs's, -10's or even -5's) your tubro shuffle, compressor surge or axi-symmetrical compressor stall (what ever the hell you want to call it) will get worse. Hence why almost all gtr's fitted with gtr's or -10's will shuffle at some point in the rev range. Get an sr20 slap on one of the said turbo's to it and you wont see that type of shuffle (2000cc displacement engine running a turbo more efficient for its displacement).

Now on how to try cure it. You can increase tge turbine housing to try slow the compressor down, (or use smaller turbos), but here you will run into another dilema, LAG. You can increase the engine displacement (why you generally wont here shuffle on a rb30/26 engine with -10's etcetc). You can try have your tuner tune it out, baffled turbo pipes etcetc. But the most effective way ive found is to use a 3 dimensional boostcontroller. Its basically an electronic controlled solenoid (by the ECM) with an rpm input ( which alters the duty cycle of the boost control valve as the RPM changes), and a throttle position sensor input (tells the turbo how much power the drive is demanding and essentially tells the turbo how much air the engine is capable of swallowing to avoid such a surge). 9 times out of 10 this will work.

p.s ( i love brackets)

[DVS JEZ]

(same)

u can also try lowering the gain setting or start boost dependong on ur boost controller. This helped with mine it makes the turbos slightly laggier but helps prevent choo choo train.

i have n1 's. Sunce changin bac to stock intakes it is gone completely

[Char]

never experienced that before.. twin turbo issue..? cant u just reach for a lower gear?

Edited January 22, 2011 by Char

[marksuxass]

never experienced that before.. twin turbo issue..? cant u just reach for a lower gear?

yep twin turbo issue. Can happen in any rev range/gear. but mainly in the high gears lower rpm/under loard

[iplen]

Is now all but gone, Ignition timing appears to have shifter (car was feeling really slow) anything upto 15degrees retarded (yes really) barely does it now